1. Field of the Invention
The present invention relates, generally, to a head restraint assembly for a vehicle seat. More specifically, the present invention relates to a cam-driven four-way head restraint assembly for a vehicle seat that provides a single control for cam-driven, four-way adjustment and incremental dual positive stops at each adjustment location.
2. Description of the Related Art
Conventional vehicle seat designs of the type commonly found in the related art typically include a seatback assembly, a lower seat assembly, recliner mechanism, manual or power adjustment mechanism for adjusting a number of positions of either the seatback or lower seat assemblies, as well as a number of safety features including occupant restraint devices such as seatbelts. The seatback assembly also includes a head restraint that is typically mounted at the top or upper end of the seatback.
Head restraint assemblies for vehicle seats are commonly known and widely used throughout the automotive industry. Head restraint assemblies generally provide comfort and support for the head of the occupant of the seat. Head restraint assemblies may also serve as a restraint to minimize the backward movement of the seat occupant's head during vehicle impact or sudden vehicle movement. In either event, head restraint assemblies are generally removably secured to the seat back through a post or posts which enable the head restraint assembly to be vertically adjusted relative to the seat back in a predetermined number of positions.
While some head restraints assemblies employ a motor for two-way vertical adjustment, manually moving the head restraint assembly is the general method for adjusting the head restraint assembly. Manual upward vertical adjustment of a head restraint assembly is generally accomplished by lifting the head restraint assembly to a desired position. However, manual downward vertical adjustment of a head restraint assembly is generally accomplished by releasing a locking mechanism which secures the head restraint assembly at a given position and then manually lowering the head restraint assembly. During vertical adjustment of the head restraint assembly, the distance between the head of the seat occupant and the head restraint assembly remains more or less the same, given the angle of the seat back relative to the seat. This distance is commonly referred to as, “backset” or “backset length.”
Head restraint assemblies having additional adjustment capabilities in the fore/aft direction relative to the head of a seat occupant are known in the related art and may provide four-way adjustment (up, down, fore and aft). Fore/aft movement may be provided to afford the seat occupant with an additional feature that allows for a more tailored seat comfort. Fore/aft adjustment of a head restraint assembly may also be included to reduce backset length, thereby further minimizing the speed and distance traveled by the head and neck in the event of a rear impact or sudden movement of the vehicle.
A number of fore/aft adjustment mechanisms for head restraint assemblies have been proposed in the related art. For example, U.S. Pat. No. 4,123,104 issued to Andres et al. on Oct. 31, 1978 employs an inflatable bellows to provide adjustable fore/aft movement of a headrest. The seat occupant is not required to manually adjust the headrest assembly, but rather engages a button or switch to control the fore/aft movement. However, the Andres et al. device requires complex components, such as a bellows and a motor to accomplish the fore/aft movement.
U.S. Pat. No. 4,861,107 issued to Vidwans et al. on Aug. 29, 1989 employs a friction hinge to provide adjustable fore/aft movement of a headrest. The Vidwans et al. device is manually adjusted by the seat occupant exerting force on the headrest to position the headrest in the desired fore or aft position. The Vidwans et al. device maintains the desired fore or aft position as a result of the tension within the friction hinge. However, the Vidwans et al. device does not provide a positive stop that secures and maintains the headrest in the desired fore or aft position during sudden movement or rear impact of a vehicle.
U.S. Pat. No. 6,000,760 issued to Chung on Dec. 14, 1999 employs an internal ratchet member to provide fore/aft adjustment of a headrest. The internal ratchet member of the Chung device is a directional locking mechanism that permits the seat occupant to manually adjust the headrest assembly in the aft direction without a positive stop at any of the predetermined fore/aft positions. To adjust the headrest from an aft position to a fore position, the headrest assembly must be fully extended in the aft direction to disengage the internal ratchet member, then returned to the foremost position to re-engage the internal ratchet member. Finally, the headrest assembly may be adjusted to the desired position. The Chung device provides a single positive stop of the headrest assembly at each of the fore/aft positions, but only in the fore direction. However, this is opposite to the direction necessary for providing restraint to the head of a seat occupant upon rear impact or other sudden forward vehicle movement. Additionally, the Chung device requires that a seat occupant undergo a series of steps to adjust the headrest assembly from an aft position to a fore position which is ergonomically undesirable.
U.S. Pat. No. 6,533,359 issued to Holstensson on Mar. 18, 2003 employs a rotatable horizontal screw to provide fore/aft movement of a headrest assembly. The rotatable screw of the Holstensson device permits a seat occupant to manually adjust the headrest assembly in either a fore or an aft direction by turning a knob behind the headrest pad, which adjusts the angle of externally located link arms that connect the headrest pad to the headrest post. While the Holstensson device may provide a positive stop of the headrest assembly in fore/aft positions, the fore/aft adjustment is limited to small incremental movements governed by the rate at which the seat occupant rotates the knob. This limitation may be ergonomically undesirable when adjusting from an aft-most position to a foremost position or vice versa. Further, the Holstensson device employs separate controls for the fore/aft movement and the vertical movement. This results in a device that is overly complex and ultimately less cost effective to assemble.
While the head restraint assemblies providing four-way adjustment of the type known in the related art have generally worked for their intended purposes, they suffer from the disadvantage that they generally fail to provide a positive stop or provide only a single positive stop or a positive stop in the opposite direction with respect to movement of the head and neck in the event of a sudden rear impact or forward acceleration. In addition, the head restraint assemblies providing four-way adjustment of the type known in the related art also suffer from undesirable ergonomic features and/or complex assemblies including motors and control components.
Thus, there remains a need in the art for a head restraint assembly that provides four-way adjustment that includes a dual positive stop for both vertical and fore/aft movement. In addition, there remains a need for a head restraint assembly providing four-way movement relative to a seat occupant having a simpler assembly and a single ergonomic control that efficiently adjusts the head restraint assembly in all four directions.